Growth failure and malnutrition are common clinical features in Alagille syndrome (AGS). The purpose of this study is descriptive in order to identify whether exocrine pancreatic insufficiency contributes to malabsorption , failure to thrive and presumed energy imbalance that are seen in children with AGS. We hypothesize that pancreatic dysfunction may contribute to the malabsorption leading to altered bone density and growth problems that are commonly seen in children with AGS. This is a twelve-month study where children will come to the hospital on three occasions. At baseline and twelve-month visit he/she will spend one night in the Clinical Research Center. The six-month visit will be an outpatient visit. During the baseline visit the following procedures will be done: anthropometry, REE, DEXA, TOBEC, bone age, direct pancreatic function test. The following labs will be drawn: hepatic function test, prealbumin, cholesterol, comprehensive metabolic panel, immunoreactive trypsinogen, Vitamin E and PT/PTT. Serum and urine from each child will be saved. After each visit we ask families to keep a three day diet record and to do a 72 hour stool collection. Stool will be analyzed for fecal fat, fecal nitrogen and fecal elastase. The six month visit consists of anthropometry and DEXA and another three day diet record and stool collection. At the 12-month visit all of the procedures (except for the direct pancreatic stimulation test) that were performed at the baseline visit will be done.